COUNT(DISTINCT) in multiple columns in SQL Server 2008 - sql-server-2008

Question

In Oracle, it's possible to get a count of distinct values in multiple columns by using the || operator (according to this forum post, anyway):
SELECT COUNT(DISTINCT ColumnA || ColumnB) FROM MyTable
Is there a way to do this in SQL Server 2008? I'm trying to perform a single query to return some group statistics, but I can't seem to do it.
For example, here is a table of values I'm trying to query:
AssetId MyId TheirId InStock
328 10 10 1
328 20 20 0
328 30 30 0
328 40 10 0
328 10 10 0
328 10 10 0
328 10 10 0
328 10 10 0
For AssetId #328, I want to compute the total number of unique IDs in the MyId and TheirId columns (4 = 10, 20, 30, 40), as well as the total number of non-zero rows in the InStock column (1):
AssetId TotalIds AvailableIds
328 4 1
Is there a way to work this magic somehow?

Answer 1

You can use a cross apply and values.
select T1.AssetId,
count(distinct T2.ID) TotalIds,
sum(case T2.InStock when 0 then 0 else 1 end) AvailableIds
from YourTable as T1
cross apply(values(T1.MyId, T1.InStock),
(T1.TheirId, 0)
) as T2(ID, InStock)
group by T1.AssetId
SE-Data
Or you can do a union all in a sub query.
select T.AssetId,
count(distinct T.ID) TotalIds,
sum(case T.InStock when 0 then 0 else 1 end) AvailableIds
from (
select AssetId, MyId as ID, InStock
from YourTable
union all
select AssetID, TheirId, 0
from YourTable
) as T
group by T.AssetId

Answer 2

I think it's good solution for you
SELECT COUNT(*)
FROM (SELECT DISTINCT Column1, Column2
FROM MyTable) A

Answer 3

You can get the result like this:
DECLARE #t TABLE (AssetId INT, MyId INT, TheirId INT, InStock INT)
INSERT #t
VALUES
(328,10, 10, 1)
,(328,20, 20, 0)
,(328,30, 30, 0)
,(328,40, 10, 0)
,(328,10, 10, 0)
,(328,10, 10, 0)
,(328,10, 10, 0)
,(328,10, 10, 0)
;WITH a AS(
SELECT AssetId,
COUNT(col) cnt
FROM
(
SELECT MyId col, AssetId
FROM #t
UNION
SELECT TheirId col, AssetId
FROM #t
) b
GROUP BY AssetId
)
SELECT a.AssetId,
a.cnt TotalIds,
SUM(CASE WHEN InStock <> 0 THEN 1 ELSE 0 END) AvailableIds
FROM #t c
JOIN a ON a.AssetId = c.AssetId
GROUP BY a.AssetId, a.cnt
In Common Table Expression (WITH code block) 'uniqueness' is guaranteed by using UNION operator which discards duplicate values, that's why COUNT(col) doesn't need to be used like COUNT(DISTINCT col).

Answer 4

You can follow the Oracle example and concatenate the values together (that is what the Oracle query is doing). You just have to convert the values to characters first:
select AssetId,
count(distinct cast(MyId as varchar(8000))+','+cast(TheirId as varchar(8000)
) totalIds,
count(distinct case when inStock> 0
then cast(MyId as varchar(8000))+','+cast(TheirId as varchar(8000)
end) as AvailableIds
from t
group by Assetid
You can also do it as a subquery:
select AssetId, count(*) as TotalIds,
sum(case when inStock > 0 then 1 else 0 end) as AvailableIds
from (select AssetId, myId, theirId, max(inStock) as inStock
from t
group by AssetId, myId, theirId
) a
group by AssetId
"Theoretically", I like the second approach better, since it is more set-based. However, if you find yourself trying to count distinct combinations columns in several different variables, the string concatenation approach is more practical.

Answer 5

If you don't like to use CTE's, you can try using following solution. The gist of it is to
select the TotalID's for each AssetID in a seperate subquery
select the AvailableIDs for each AssetID in a seperate subquery
JOIN the results of both subqueries to produce the final results.
The statement as is works on the entire table. You can get the results for a single AssetID by adding an appropriate where clause to the entire group.
SQL Statement
SELECT a.AssetId, t.TotalIDs, a.AvailableIDs
FROM (
SELECT AssetID, TotalIDs = COUNT(*)
FROM (
SELECT AssetID
FROM MyTable
GROUP BY
MyId, TheirID, AssetID
) t
GROUP BY
AssetID
) AS t
INNER JOIN (
SELECT AssetID, AvailableIDs = SUM(InStock)
FROM MyTable
GROUP BY
AssetID
) AS a ON a.AssetId = t.AssetId
Test script
;WITH MyTable (AssetId, MyId, TheirId, InStock) AS (
SELECT * FROM (VALUES
(328, 10, 10, 1)
, (328, 20, 20, 0)
, (328, 30, 30, 0)
, (328, 40, 10, 0)
, (328, 10, 10, 0)
, (328, 10, 10, 0)
, (328, 10, 10, 0)
, (328, 10, 10, 0)
, (329, 10, 10, 0)
, (329, 10, 20, 1)
) AS a (b, c, d, e)
)
SELECT a.AssetId, t.TotalIDs, a.AvailableIDs
FROM (
SELECT AssetID, TotalIDs = COUNT(*)
FROM (
SELECT AssetID
FROM MyTable
GROUP BY
MyId, TheirID, AssetID
) t
GROUP BY
AssetID
) AS t
INNER JOIN (
SELECT AssetID, AvailableIDs = SUM(InStock)
FROM MyTable
GROUP BY
AssetID
) AS a ON a.AssetId = t.AssetId

Answer 6

Option #1
select
AssetID, count(distinct MyId) As MyId, SUM(InStock) InStock
From T
Group By
AssetID
Option #2 Without CTE
Select AssetID, count(MyId), sum(InStock) InStock From
(
select
AssetID, MyId, SUM(InStock) InStock
From MyTable
Group By
AssetID, MyId
)K
Group by AssetID
Option #3 With CTE
;With Sub(AssetID, MyId, InStock)
As
(
select
AssetID, MyId, SUM(InStock) InStock
From MyTable
Group By
AssetID, MyId
)
Select AssetID, count(MyId), sum(InStock) From
(
Select * from Sub
)K